The present disclosure relates to the field of organic light-emitting display, and more particularly, to a power supply circuit, an array substrate, and a display device.
Currently, Organic Light-emitting Diode (OLED) display is a new and very popular flat panel display at home and abroad. The OLED display has characteristics of self light-emitting, wide viewing angle, short response time, high light-emitting efficiency, wide color gamut, low operating voltage, thin panel, being suitable for producing large-size and flexible panels, simple production process, and the like. The OLED display also has potential to be produced at low cost.
In an OLED display, a driving current is typically provided to a plurality of pixel units in a row through the same power wire. FIG. 1 is an exemplary schematic diagram of a power supply circuit. As shown in FIG. 1, a power supply VDD drives a plurality of active matrix organic light-emitting diodes (AMOLED) D1, D2, D3, and D4 through one power wire. The resistance symbols in FIG. 1 represent the equivalent resistance of each segment of the power wires.
When a row of pixel units all emit light, for example, when the organic light-emitting diodes D1, D2, D3, and D4 all emit light, in the power wire in the backplane of the display, the voltage at a position near the power supply VDD is higher than the voltage at a position far from the power supply VDD, due to the resistances of the power wires. This phenomenon is called voltage drop (IR drop). Due to the effect of voltage drop, the luminance of the pixel at the position near the power supply VDD is higher than that of the pixel at the position far from the power supply VDD. That is, if the light-emitting diodes D1, D2, D3, and D4 emit light simultaneously, since the light-emitting diode D1 is at a position near the power supply VDD, the voltage across the light-emitting diode D1 is larger and the luminance is higher.
When part of a row of pixel units emit light, for example, when the light-emitting diodes D1 and D4 emit light but the light-emitting diodes D2 and D3 do not emit light or the current flowing to D2 and D3 is extremely small (extremely weakly emitting light), the current flowing to the light-emitting diode D4 increases so that the light-emitting luminance of the light-emitting diode D1 is also different from that of the light-emitting diode D4.
Therefore, in display applications, in the above two cases, different light-emitting diodes will have a difference in luminance, resulting in nonuniform luminance and the occurrence of various traces (i.e. mura phenomenon) in a display.
FIG. 2 is a schematic diagram for explaining the phenomenon of nonuniform display luminance. In FIG. 2, each area may include a plurality of rows of pixel units. Area 2 is located at a position near the power supply VDD, and area 4 is located at a position far from the power supply VDD. In combination with FIG. 1, it is assumed that the area 2 includes a light-emitting diode D1, the area 3 includes light-emitting diodes D2, D3, and the area 4 includes a light-emitting diode D4. And it is assumed that the pixel units in the area 1 all emit light, namely, the area 1 is a light-emitting area. It is also assumed that the light-emitting diode D1 in the area 2 emits light, and then the area 2 is a light-emitting area. The light-emitting diodes D2 and D3 in the area 3 do not emit light, and then the area 3 is a dark area. The light-emitting diode D4 in the area 4 emits light, and then the area 4 is a light-emitting area.
According to the above described analysis, in FIG. 2, the pixel units in the area 1 all emit light. However, due to the presence of resistance of the power wire, the light-emitting luminance of the area 1 gradually decreases from the position near the power supply VDD to the position far from the power supply VDD. In addition, since the area 3 is dark, the area 2 is brighter than the area 1, and the area 4 is higher in the light-emitting luminance than the area 1 due to the larger incoming current. This will lead to the phenomenon of nonuniform light-emitting luminance in the display.